Fucoidans and laminarins are natural polysaccharides present in the extracellular matrix of brown seaweeds (Phaeophyceae). Fucoidans primarily contain L-fucose and ester sulfate groups, with lesser amounts of other monosaccharides such as galactose, glucose, mannose, xylose, and arabinose; uronic acids such as glucuronic acid; cations such as sodium, potassium, calcium, and magnesium; and protein. Laminarins are linear glucans (i.e., polysaccharides based on glucose). Alternate names for fucoidan include fucoidin, fucan, fucosan, and sulphated fucan; alternate names for laminarin include laminaran, storage glucan, and beta glucan.
The molecular structures of fucoidan can vary somewhat depending on the algae. Although each seaweed species comprises a unique individual fucoidan, there is at least one important compositional feature that all fucoidans have in common; i.e., the primary components are always L-fucose and ester sulphate with the ester sulphate residues always being on the polyfucan molecular backbone. Depending on manufacturing methods, components other than sulphated polyfucan are often included with the fucoidan. Such additional components include neutral monosaccharides, such as galactose, glucose, mannose, xylose, arabinose and rhamnose; uronic acids, such as glucuronic acid; cations, such as sodium, potassium, calcium and magnesium; and protein. The molecular backbone of fucoidan molecules is linear α-L-fucose, but the overall structure has extensive branching, which may include additional L-fucose in addition to the other components mentioned above. The ester sulphate groups are on L-fucose units, but not all L-fucose units are sulphated, and the distribution of these ester sulphates varies by species, by location, and by season. Similarly, some fucoidans are partially acetylated on the fucose backbone, and the distribution of these O-acetyl groups can vary by species, by location, and by season.
The molecular structures of laminarins are less complex than fucoidans, and they are β-glucans comprising mostly 1-3 linkages, but also with occasional 1-6 linkages to interrupt complete linearity. The structure of laminarin varies by species, by location, and by season.
Fucoidans and laminarins have been extensively studied for their biological activities, including anticoagulant, antithrombotic, antivirus, antitumor, anticomplementary, immunomodulatory, anti-inflammatory, blood lipid reducing, antioxidant, activity against hepatopathy, uropathy and renalpathy, gastric protective effects, and therapeutic potential in surgery.
Conventional processes for extracting fucoidan from seaweed do not utilize exudation, but instead involve complicated chemical and mechanical extraction steps that have been taught to be critical. For example, Holtcamp, et al., APPL Microbiol Biotechnol (2009), 82, 1-11, teaches the use of chemical and mechanical extraction processes from dried seaweed as being critical to get suitable amounts for structural categorization of fucoidan.
US 2009/0170810 teaches chemical extraction, purification and fractionating steps for obtaining fucoidan from seaweed. For example, water, diluted acid or calcium chloride solution is added to the seaweed, then lead hydroxide, aluminum hydroxide, ethanol or quaternary ammonium salts or cationic surfactants are added to precipitate the fucoidan. The crude fucoidan often contains alginate, proteins, laminarin, and pigments. As such, the crude fucoidan is further extracted with hot water and ethanol in the presence of magnesium chloride.
US 2009/0105190 discloses the addition of ethanol to the raw alga body of Cladosiphon, removal of the ethanol, followed by hot water extraction comprising the addition of sufficient amounts of water and hydroxides to the extract. The temperature of the hot water extraction is preferably from 70 to 100° C. for 0.5 to 2 hours. The use of ethanol in this process dehydrates the fresh seaweed and removes color. Exudation will not occur in such a process as the ethanol would tighten the seaweed structure and “pores” preventing exudation. Hot water is then necessary to release the fucoidan into solution by breaking down the tightened seaweed structure.
There is a desire to use simpler processes for isolating fucoidan and laminarin from seaweed that produce commercial quantities of fucoidan and laminarin in pure form (i.e., fucoidan and laminarin that are not degraded and depolymerized by acid treatment, alkali treatment or thermal treatment).
As the present invention obtains the fucoidan and laminarin from the exudate of live, harvested seaweeds in purity and yield levels suitable for commercial manufacture, the significantly more complicated and costly chemical extraction methods heretofore known and used are not necessary or desired.